A 16-kg sled is being pulled along the horizontal snow-covered ground by a horizontal force of 35 N. Starting from rest, the sled attains a speed of 2.1 m/s in 9.5 m. Find the coefficient of kinetic friction between the runners of the sled and the snow.

Answer 1

35 - ckf * 16 = m*a

where ckf is coefficient of kinetic friction. In your textbook ckf is probably represented as the greek letter mu, but it's really hard to write greek letters here. . .
m is the mass of the sled, and a is its acceleration.

x = 1/2 * a * t^2
v = a * t

where x is the distance traveled by the sled, t is time, and v is the speed

so

9.5 = 1/2 * a * t^2
2.1 = a * t

Using algebra:

t = 2.1/a
plugging into the equation for x:

9.5 = (1/2 * 2.1^2)/a

Use algebra to solve for the acceleration, then plug into

35 - ckf * 16 = 16*a

and solve for ckf